Amorphous steels are extremely hard materials and have presented considerable problems in shear-cutting because of excessive wear of the blades used for effecting the shear-cutting. Such wear is characterized by the blades either becoming dull or chipping or both as the shear-cutting operations are repeated over and over again.
In U.S. Pat. No. 4,942,798-Taub et al, assigned to the assignee of the present invention and incorporated by reference herein, there is disclosed and claimed an improved form of shear-cutting apparatus that is characterized by reduced blade-wear as compared to prior shear-cutting apparatus. Taub et al achieve their improved results by using a special design of the shearing blades in which one or both of the blades has a negative rake angle. The blade material used by Taub et al is described in the patent as a conventional hard cutting material, such as cemented tungsten carbide. Specific materials disclosed are Carboloy Grades 895 and 883, which are cemented tungsten carbides containing 6 percent cobalt.
Taub et al describe one series of tests with such blades in which stacks of Allied-Signal Corporation's Metglas 2605-S2 amorphous steel, each stack containing 10 superposed strips, each strip about 0.001 inch thick, were shear cut with the blades until a blade failure occurred. Sixty thousand cuts of these 10-strip-thick stacks were achieved before a blade failure occurred.
While these results are quite good compared to those that had been achieved with prior shear-cutting apparatus, it should be noted that if the number of amorphous steel strips in each stack is increased to substantially greater than ten, there is a substantial decrease in blade life. For example, if the stack thickness is increased from ten to fifteen strips, the number of cuts that can be achieved before blade failure (using the blade design and blade materials disclosed in the Taub et al patent) decreases to an average of less than 10,000. There is a distinct need for blades that can shear-cut amorphous steel stacks of this increased thickness (i.e., 15 strips) with a greater number of cuts before any blade failure occurs.